Add half of the milk; add the remaining 2 cups of powdered sugar and beat well; add more milk as necessary to reach desired consistency

When the cake is done remove from the oven and immediately spread the marshmallow cream over the top; microwave the marshmallow cream before spreading it, remove all foil and microwave for 15 second intervals until it starts to puff up over the edge of jar

Spread the frosting over the warm cake and marshmallow cream; use a spatula or knife to swirl it